A solution having suitable chromatic and thermal correction for thermal image apparatus in the spectral range from approximately 7.5 .mu.m to 10.5 .mu.m and only four to five lenses is disclosed in United States patent application 08/780,295, filed Jan. 8, 1997, incorporated herein by reference. Here, chalcogenide glasses and aspheric surfaces are provided.
U.S. Pat. No. 5,044,706 discloses a telescope suitable for the same use. An intermediate image is provided with four lenses for the far viewing field. Thus, a reimager is provided. A telescope without an intermediate image is realized with only two lenses thereof. The front lenses both have aspheric surfaces on different sides and a diffractive kinoform surface. Nothing is suggested as to athermalization.